This invention relates to a gas circuit breaker and, more particularly, to an improvement in a double flow type circuit breaker assembly indispensable to large-capacity circuit breakers.
To reduce the operating force of puffer type circuit breakers most popularly used for such a gas circuit breakers, self extinction combination design is ordinarily adopted whereby arc heat is positively utilized to increase the gas pressure and to thereby reduce the external operating force for gas compression. Also, for puffer type circuit breakers, a double flow method of blowing a pressurized gas to both the fixed side and the movable side is indispensable to large-current breaking.
In view of these circumstances, a double-flow puffer type circuit breaker has been proposed in which a gas pressurized by arc heat is effectively blown to the arc, and which is disclosed in U.S. Ser. No. 07/543,440 filed by the inventors of the present invention.
The circuit breaker described in U.S. Ser. No. 07/543,440 has a main fixed element and a main movable element as a main conductive part, a fixed contact provided on the main fixed element side, a movable contact provided on the main movable element side and capable of contacting and moving apart from the fixed contact, an insulation nozzle provided on the main movable element side to surround these contacts, a hollow nozzle provided inside the movable contact, a cylinder and a puffer cylinder on which the main movable element, the movable contact, the insulation nozzle and other members are fixed, and a fixed piston which, together with the puffer cylinder, defines a puffer chamber. A gas flow passage is formed in the hollow nozzle and has an opening in a side surface of the cylinder. An exhaust guide which closes this opening until the breaker is set in a suitable breaking position is formed on the periphery of the cylinder. However, the gas circuit breaker described in the prior application entails the problem of difficulty in inspecting the interior of the circuit breaker through a hand hole or the like of the casing in which the circuit breaker is housed, as well as in disassembling or assembling the fixed contact, the movable contact, the insulation nozzle and other members, because the exhaust guide is provided on the periphery of the cylinder.